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tok.c

/***********************************************************************
*                                                                      *
*               This software is part of the ast package               *
*          Copyright (c) 1985-2008 AT&T Intellectual Property          *
*                      and is licensed under the                       *
*                  Common Public License, Version 1.0                  *
*                    by AT&T Intellectual Property                     *
*                                                                      *
*                A copy of the License is available at                 *
*            http://www.opensource.org/licenses/cpl1.0.txt             *
*         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
*                                                                      *
*              Information and Software Systems Research               *
*                            AT&T Research                             *
*                           Florham Park NJ                            *
*                                                                      *
*                 Glenn Fowler <gsf@research.att.com>                  *
*                  David Korn <dgk@research.att.com>                   *
*                   Phong Vo <kpv@research.att.com>                    *
*                                                                      *
***********************************************************************/
#pragma prototyped
/*
 * Glenn Fowler
 * AT&T Research
 *
 * token stream routines
 */

#include <ast.h>
#include <tok.h>

#define FLG_RESTORE     01          /* restore string on close    */
#define FLG_NEWLINE     02          /* return newline token next  */

typedef struct Tok_s                /* token stream state         */
{
      union
      {
      char*       end;        /* end ('\0') of last token   */
      struct Tok_s*     nxt;        /* next in free list          */
      }           ptr;
      char        chr;        /* replace *end with this     */
      char        flg;        /* FLG_*                */
} Tok_t;

static Tok_t*           freelist;

/*
 * open a new token stream on s
 * if f==0 then string is not restored
 */

char*
tokopen(register char* s, int f)
{
      register Tok_t*   p;

      if (p = freelist)
            freelist = freelist->ptr.nxt;
      else if (!(p = newof(0, Tok_t, 1, 0)))
            return 0;
      p->chr = *(p->ptr.end = s);
      p->flg = f ? FLG_RESTORE : 0;
      return (char*)p;
}

/*
 * close a token stream
 * restore the string to its original state
 */

void
tokclose(char* u)
{
      register Tok_t*   p = (Tok_t*)u;

      if (p->flg == FLG_RESTORE && *p->ptr.end != p->chr)
            *p->ptr.end = p->chr;
      p->ptr.nxt = freelist;
      freelist = p;
}

/*
 * return next space separated token
 * "\n" is returned as a token
 * 0 returned when no tokens remain
 * "..." and '...' quotes are honored with \ escapes
 */

char*
tokread(char* u)
{
      register Tok_t*   p = (Tok_t*)u;
      register char*    s;
      register char*    r;
      register int      q;
      register int      c;

      /*
       * restore string on each call
       */

      if (!p->chr)
            return 0;
      s = p->ptr.end;
      switch (p->flg)
      {
      case FLG_NEWLINE:
            p->flg = 0;
            return "\n";
      case FLG_RESTORE:
            if (*s != p->chr)
                  *s = p->chr;
            break;
      default:
            if (!*s)
                  s++;
            break;
      }

      /*
       * skip leading space
       */

      while (*s == ' ' || *s == '\t')
            s++;
      if (!*s)
      {
            p->ptr.end = s;
            p->chr = 0;
            return 0;
      }

      /*
       * find the end of this token
       */

      r = s;
      q = 0;
      for (;;)
            switch (c = *r++)
            {
            case '\n':
                  if (!q)
                  {
                        if (s == (r - 1))
                        {
                              if (!p->flg)
                              {
                                    p->ptr.end = r;
                                    return "\n";
                              }
                              r++;
                        }
                        else if (!p->flg)
                              p->flg = FLG_NEWLINE;
                  }
                  /*FALLTHROUGH*/
            case ' ':
            case '\t':
                  if (q)
                        break;
                  /*FALLTHROUGH*/
            case 0:
                  if (s == --r)
                  {
                        p->ptr.end = r;
                        p->chr = 0;
                  }
                  else
                  {
                        p->chr = *(p->ptr.end = r);
                        if (*r)
                              *r = 0;
                  }
                  return s;
            case '\\':
                  if (*r)
                        r++;
                  break;
            case '"':
            case '\'':
                  if (c == q)
                        q = 0;
                  else if (!q)
                        q = c;
                  break;
            }
}

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